Retransmission method for dynamic subframe setting in wireless communication system and apparatus for same

ABSTRACT

Disclosed is a method for allowing a terminal to transmit and receive signals to and/from a base station in a wireless communication system using a time division multiplexing method. Specifically, the method comprises the steps of: receiving a request signal for resetting into a second uplink/downlink setting while transmitting and receiving a signal according to a first uplink/downlink setting; terminating an uplink retransmission process associated with a specific uplink subframe when the use of the specific uplink subframe is changed into a downlink subframe according to the second uplink/downlink setting; and applying the second uplink/downlink setting at a specific time point to transmit and receive signals.

This application is a continuation of U.S. application Ser. No.14/002,017 filed on Aug. 28, 2013, now allowed, which is a 35 U.S.C. §371 National Stage entry of International Application No.PCT/KR2012/001666 filed on Mar. 7, 2012, which claims priority to U.S.Provisional Application No. 61/466,917, filed Mar. 23, 2011; and61/472,610 filed Apr. 6, 2011, all of which are incorporated byreference in their entirety herein.

FIELD OF THE INVENTION

Embodiments of the present invention relate to a wireless communicationsystem, and more particularly to a retransmission method and apparatusused in the case in which a dynamic subframe is established in thewireless communication system.

BACKGROUND ART

As a representative example of a wireless communication system of thepresent invention, 3^(rd) Generation Partnership Project Long TermEvolution (3GPP LTE) and LTE-Advanced (LTE-A) communication systems willhereinafter be described in detail.

FIG. 1 is a conceptual diagram illustrating an Evolved Universal MobileTelecommunications System (E-UMTS) network structure as an exemplarymobile communication system. In particular, the Enhanced UniversalMobile Telecommunications System (E-UMTS) has evolved from a legacy UMTSsystem, and basic standardization thereof is now being conducted by the3rd Generation Partnership Project (3GPP). E-UMTS may also be referredto as Long Term Evolution (LTE). For details of the technicalspecifications of UMTS and E-UMTS, refer to Release 7 and Release 8 of“3rd Generation Partnership Project; Technical Specification Group RadioAccess Network”.

As shown in FIG. 1, the E-UMTS system is broadly made up of a UserEquipment (UE) 120, base stations (or eNode-Bs) 110 a and 110 b, and anAccess Gateway (AG) which is located at an end of a network (E-UTRAN)and is connected to an external network. Generally, an eNode-B cansimultaneously transmit multiple data streams for a broadcast service, amulticast service and/or a unicast service.

Each eNode-B includes one or more cells. One cell of the eNode-B is setto use a bandwidth such as 1.25, 2.5, 5, 10, 15 or 20 MHz to provide adownlink or uplink transmission service to user equipments (UEs). Here,different cells may be set to use different bandwidths. The eNode-Bcontrols transmission and reception of data for several UEs. Inassociation with downlink (DL) data, the eNode-B transmits downlink (DL)scheduling information to a corresponding UE, so as to inform thecorresponding UE of time/frequency domains where data is to betransmitted, coding information, data size information, Hybrid AutomaticRepeat and reQuest (HARQ)—related information, and the like. Inassociation with uplink (UL) data, the eNode-B transmits UL schedulinginformation to the corresponding UE, so that it informs thecorresponding UE of time/frequency domains capable of being used by thecorresponding UE, coding information, data size information,HARQ-related information, and the like. An interface for transmission ofuser traffic or control traffic may be used between eNode-Bs. A CoreNetwork (CN) may include an Access Gateway (AG) and a network node foruser registration of the UE. The AG manages mobility of a UE on thebasis of a Tracking Area (TA) composed of several cells.

Although wireless communication technology has been developed to LTEtechnology on the basis of WCDMA technology, users and enterprisescontinuously demand new features and services. In addition, otherwireless access technologies are being developed, such that there is aneed for new or improved wireless access technology in order to remaincompetitive in the long run. For example, reduction in cost per bit,increase of service availability, adaptive frequency band utilization, asimple structure, an open-type interface, and appropriate user equipment(UE) power consumption are needed for new or improved wireless accesstechnology.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

Accordingly, the present invention is directed to a retransmissionmethod and apparatus used in the case in which a dynamic subframe isestablished in a wireless communication system.

Technical Solution

The object of the present invention can be achieved by providing amethod for transmitting/receiving a signal to/from a base station (BS)by a user equipment (UE) in a time division multiplexing (TDM) wirelesscommunication system, the method including: receiving a reconfigurationrequest signal for a second uplink(UL)/downlink(DL) configuration whilesignals are transmitted/received according to a first UL/DLconfiguration; if a use of a specific uplink (UL) subframe is changed toa use of a downlink (DL) subframe by the second UL/DL configuration,terminating an uplink (UL) retransmission process associated with thespecific UL subframe; and transmitting/receiving signals using thesecond UL/DL configuration at a specific time. The reconfigurationrequest signal may be received through a higher layer.

The termination of the UL retransmission process may include: setting aresponse of a signal transmitted to the specific UL subframe to anacknowledgment (ACK). The method may further include: receiving a signalindicating deactivated decoding of a response of the signal transmittedto the specific UL subframe.

The method may further include: receiving information regarding anapplication timing point of the second UL/DL configuration.

In accordance with another aspect of the present invention, a userequipment (UE) device for use in a time division multiplexing (TDM)wireless communication system includes: a radio frequency (RF)communication module configured to receive a reconfiguration requestsignal for a second uplink(UL)/downlink(DL) configuration while signalsare transmitted/received according to a first UL/DL configuration; and aprocessor, if a use of a specific uplink (UL) subframe is changed to ause of a downlink (DL) subframe by the second UL/DL configuration,configured to terminate an uplink (UL) retransmission process associatedwith the specific UL subframe, wherein the processor controls the RFcommunication module to transmit/receive signals using the second UL/DLconfiguration at a specific time.

The processor may set a response of a signal transmitted to the specificUL subframe to an acknowledgment (ACK) so as to terminate the ULretransmission process. The RF communication module may receive a signalindicating deactivated decoding of a response of the signal transmittedto the specific UL subframe.

The RF communication module may receive information regarding anapplication timing point of the second UL/DL configuration.

The second UL/DL configuration may include a combination of one or moreUL/DL configurations, and the reconfiguration request signal may includea combination of the one or more UL/DL configurations and specificinformation regarding a length of the combination.

Effects of the Invention

As is apparent from the above description, according to exemplaryembodiments of the present invention, a retransmission operation can beefficiently performed when a dynamic subframe is allocated in a wirelesscommunication system.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present invention are not limited to whathas been particularly described hereinabove and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram illustrating an Evolved Universal MobileTelecommunications System (E-UMTS) network structure as an example of awireless communication system.

FIG. 2 illustrates a control plane and a user plane (U-Plane) of a radiointerface protocol between a User Equipment (UE) and an E-UTRANaccording to the 3GPP wireless access network standard.

FIG. 3 is a conceptual diagram illustrating physical channels used in a3GPP LTE system as an exemplary mobile communication system and ageneral method for transmitting a signal using the physical channels.

FIG. 4 is a diagram illustrating a structure of a radio frame for use ina Long Term Evolution (LTE) system.

FIG. 5 is a conceptual diagram illustrating a downlink radio frame foruse in an LTE system.

FIG. 6 shows a resource unit used when a control channel is constructed.

FIG. 7 shows an example for distributing CCEs to a system band.

FIG. 8 shows an uplink subframe structure for use in the LTE system.

FIG. 9 shows an example of implementing a subframe dynamic changethrough dedicated RRC signaling in an LTE TDD system.

FIG. 10 shows an example of using an uplink HARQ operation according toa first embodiment.

FIG. 11 shows an example of using an uplink HARQ operation according toa second embodiment.

FIG. 12 shows an example of dynamically changing UL/DL configurationaccording to a third embodiment.

FIG. 13 is a block diagram illustrating a communication device accordingto embodiments of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. The aboveand other configurations, operations, and features of the presentinvention will be easily understood from the embodiments of theinvention described below with reference to the accompanying drawings.The embodiments described below are examples wherein technical featuresof the invention are applied to a 3^(rd) Generation Partnership Project(3GPP) system.

Although the embodiment of the present invention will be disclosed onthe basis of an LTE system and an LTE-A system for convenience ofdescription and better understanding of the present invention, it shouldbe noted that the scope or spirit of the present invention is notlimited thereto and can be applied to other communication systems asnecessary.

FIG. 2 illustrates a control plane and a user plane (U-Plane) of a radiointerface protocol between a User Equipment (UE) and an E-UTRANaccording to the 3GPP wireless access network standard. The controlplane is a passage through which control messages that a UE and anetwork use in order to manage calls are transmitted. The user plane isa passage through which data (e.g., voice data or Internet packet data)generated at an application layer is transmitted.

The physical layer, which is the first layer, provides an informationtransfer service to an upper layer using a physical channel. Thephysical layer is connected to a Medium Access Control (MAC) layer,located above the physical layer, through a transport channel. Data istransferred between the MAC layer and the physical layer through thetransport channel. Data transfer between different physical layers,specifically between the respective physical layers of transmitting andreceiving sides, is performed through the physical channel. The physicalchannel uses time and frequency information as radio resources. In moredetail, using the time and frequency information as radio resources, thephysical channel is modulated according to the Orthogonal FrequencyDivision Multiple Access (OFDMA) scheme via a downlink, and is modulatedaccording to the Single Carrier Frequency Division Multiple Access(SC-FDMA) scheme via an uplink.

The MAC layer of the second layer provides a service to a Radio LinkControl (RLC) layer, located above the MAC layer, through a logicalchannel. The RLC layer of the second layer enhances data transmissionreliability. The functions of the RLC layer may also be implementedthrough internal functional blocks of the MAC layer. A PDCP layer of thesecond layer performs a header compression function to reduceunnecessary control information in order to efficiently transmit IPpackets such as IPv4 or IPv6 packets over a radio interface with arelatively narrow bandwidth.

A Radio Resource Control (RRC) layer located at the lowest part of thethird layer is defined only in the control plane and is responsible forcontrol of logical, transport, and physical channels in association withconfiguration, re-configuration and release of Radio Bearers (RBs). Theradio bearer (RB) is a service that the second layer provides for datacommunication between the UE and the network. To accomplish this, theRRC layer of the UE and the RRC layer of the network exchange RRCmessages. The UE is in RRC connected mode if an RRC connection has beenestablished between the RRC layer of the network and the RRC layer ofthe UE. Otherwise, the UE is in RRC idle mode. A Non-Access Stratum(NAS) layer located above the RRC layer performs functions such assession management and mobility management.

One cell of the eNB (eNode-B) is set to use a bandwidth such as 1.25,2.5, 5, 10, 15 or 20 MHz to provide a downlink or uplink transmissionservice to UEs. Here, different cells may be set to use differentbandwidths.

Downlink transport channels for transmission of data from the network tothe UE include a Broadcast Channel (BCH) for transmission of systeminformation, a Paging Channel (PCH) for transmission of paging messagesand a downlink Shared Channel (SCH) for transmission of user traffic orcontrol messages. User traffic or control messages of a downlinkmulticast or broadcast service may be transmitted through a downlink SCHand may also be transmitted through a downlink multicast channel (MCH).Uplink transport channels for transmission of data from the UE to thenetwork include a Random Access Channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels, which are located abovethe transport channels and are mapped to the transport channels, includea Broadcast Control Channel (BCCH), a Paging Control Channel (PCCH), aCommon Control Channel (CCCH), a Multicast Control Channel (MCCH) and aMulticast Traffic Channel (MTCH).

FIG. 3 is a conceptual diagram illustrating physical channels for use ina 3GPP system and a general method for transmitting a signal using thephysical channels.

Referring to FIG. 3, when powered on or when entering a new cell, a UEperforms initial cell search in step S301. The initial cell searchinvolves synchronization with a BS. Specifically, the UE synchronizeswith the BS and acquires a cell Identifier (ID) and other information byreceiving a Primary Synchronization CHannel (P-SCH) and a SecondarySynchronization CHannel (S-SCH) from the BS. Then the UE may acquireinformation broadcast in the cell by receiving a Physical BroadcastCHannel (PBCH) from the BS. During the initial cell search, the UE maymonitor a downlink channel status by receiving a downlink ReferenceSignal (DL RS).

After the initial cell search, the UE may acquire more specific systeminformation by receiving a Physical Downlink Control CHannel (PDCCH) andreceiving a Physical Downlink Shared CHannel (PDSCH) based oninformation of the PDCCH in step S302.

On the other hand, if the UE initially accesses the BS or if the UE doesnot have radio resources for signal transmission, it may perform arandom access procedure to the BS in steps S303 to S306. For the randomaccess, the UE may transmit a predetermined sequence as a preamble tothe BS on a Physical Random Access CHannel (PRACH) in steps S303 andS305 and receive a response message for the random access on a PDCCH anda PDSCH corresponding to the PDCCH in steps S304 and S306. In the caseof contention-based RACH, the UE may perform a contention resolutionprocedure.

After the foregoing procedure, the UE may receive a PDCCH and a PDSCH instep S307 and transmit a Physical Uplink Shared CHannel (PUSCH) and aPhysical Uplink Control CHannel (PUCCH) in step S308, as a generaldownlink/uplink (DL/UL) signal transmission procedure. Specifically, theUE may receive downlink control information (DCI) through a PDCCH. Inthis case, DCI includes control information such as resource allocationinformation for the UE, and has different formats according to usagepurposes.

On the other hand, uplink control information transmitted from the UE tothe BS or downlink control information transmitted from the UE to the BSmay include a downlink (DL) or uplink (UL) ACKnowledgement/NegativeACKnowledgment (ACK/NACK) signal, a Channel Quality Indicator (CQI), aPrecoding Matrix Index (PMI) and/or a Rank Indicator (RI). The UEadapted to operate in the 3GPP LTE system may transmit the controlinformation such as a CQI, a PMI, and/or an RI on the PUSCH and/or thePUCCH.

FIG. 4 is a diagram illustrating a structure of a radio frame used in anLTE system.

Referring to FIG. 4, the radio frame has a length of 10 ms (327200·TOand includes 10 subframes of equal size. Each subframe has a length of 1ms and includes two slots. Each slot has a length of 0.5 ms(15360·T_(s)). In this case, T_(s) represents sampling time, and isexpressed by ‘T_(s)=1/(15 kHz×2048)=3.2552×10⁻⁸ (about 33 ns)’. The slotincludes a plurality of OFDM symbols in a time domain, and includes aplurality of resource blocks (RBs) in a frequency domain. In the LTEsystem, one resource block includes twelve (12) subcarriers×seven (orsix) OFDM (Orthogonal Frequency Division Multiplexing) symbols. ATransmission Time Interval (TTI) which is a transmission unit time ofdata can be determined in a unit of one or more subframes. Theaforementioned structure of the radio frame is only exemplary, andvarious modifications can be made to the number of subframes containedin the radio frame or the number of slots contained in each subframe, orthe number of OFDM symbols in each slot.

FIG. 5 shows a control channel contained in a control region of onesubframe in a downlink radio frame according to one embodiment of thepresent invention.

Referring to FIG. 5, one subframe includes 14 OFDM symbols. First tothird ones of the 14 OFDM symbols may be used as a control region, andthe remaining OFDM symbols (i.e., 11 to 13 OFDM symbols) may be used asa data region. In FIG. 5, R1 to R4 represent reference signals (RSs)(also called pilot signals) of antennas 0 to 3, respectively. In ageneral subframe, RSs of the antennas 0 to 3 are fixed to apredetermined pattern irrespective of a control region and a dataregion. The control channel is allocated to a resource, to which the RSis not allocated, in the control region. A traffic channel is allocatedto a resource, to which the RS is not allocated, in the data region. Avariety of control channels may be allocated to the control region, forexample, a physical control format indicator channel (PCFICH), aphysical hybrid-ARQ indicator channel (PHICH), a physical downlinkcontrol channel (PDCCH), etc.

PCFICH is used as a physical control format indicator channel, andinforms the UE of the number of OFDM symbols used for PDCCH at everysubframe. PCFICH is located at a first OFDM symbol, and is establishedto have priority over PHICH and PDCCH. PCFICH includes 4 resourceelement groups (REGs), and individual REGs are distributed into thecontrol region on the basis of a cell ID. One REG includes four REs. TheRE is a minimum physical resource defined by ‘one subcarrier×one OFDMsymbol’. The PCFICH value indicates values of 1 to 3 or values of 2 to 4according to bandwidth, and is QPSK (Quadrature Phase ShiftKeying)—modulated.

PHICH is used as a physical HARQ (Hybrid-Automatic Repeat and reQuest)indicator channel, and carries HARQ ACK/NACK signals for uplinktransmission. In other words, PHICH indicates a channel for transmittingDL ACK/NACK information for UL HARQ. The PHICH includes one REG, and iscell-specifically scrambled. An ACK/NACK signal indicated by one bit isBPSK (Binary Phase Shift Keying)—modulated. The modulated ACK/NACK isspread with a spreading factor (SF) of 2 or 4. Several PHICHs mapped tothe same resources construct a PHICH group. The number of PHICHsmultiplexed in the PHICH group may be determined according to the numberof spreading codes. PHICH (or PHICH group) may be repeated three timesso as to obtain a diversity gain from a frequency domain and/or a timedomain.

PDCCH acting as a physical downlink control channel is allocated to Nfirst OFDM symbols of a subframe. In this case, N is an integer of 1 orhigher and is indicated by a PCFICH. PDCCH includes one or more CCEs.PDCCH may inform each UE or a UE group of information related toresource allocation of PCH (Paging Channel) and DL-SCH (Downlink-sharedchannel), uplink scheduling grant, HARQ information, etc. The PCH andthe DL-SCH are transmitted through a PDSCH. Therefore, the BS and the UEmay transmit and receive data other than either specific controlinformation or specific service data through the PDSCH.

Information indicating which UE will receive data as an input,information indicating how the UEs receive PDSCH data, and informationindicating whether decoding is carried out are contained in the PDCCH.For example, it is assumed that a specific PDCCH is CRC-masked with aRadio Network Temporary Identity (RNTI) called ‘A’, and information thatis transmitted using radio resources ‘B’ (for example, a frequencylocation) and transmission format information ‘C’ (for example, atransmission block size, a modulation scheme, coding information, etc.),is transmitted through a specific subframe. In this case, a UE locatedin a cell monitors a PDCCH using its own RNTI information. If at leastone UE having the RNTI ‘A’ is present, the UEs receive PDCCH and receivePDSCH indicated by ‘B’ and ‘C’ through the received PDCCH information.

FIG. 6 is a diagram showing a resource unit used for configuring acontrol channel. FIG. 6(a) shows the case where the number oftransmission antennas is 1 or 2 and FIG. 6(b) shows the case where thenumber of transmission antennas is 4, which are different from eachother in only an RS pattern according to the number of transmissionantennas, but are equal to each other in a method of setting a resourceunit associated with the control channel.

Referring to FIGS. 6(a) and 6(b), the REG which is the basic resourceunit of the control channel is composed of four neighbor REs in a stateof excluding the RS. The REG is denoted by a thick line in the drawing.The PCFICH and the PHICH include four REGs and three REGs, respectively.The PDCCH is composed of CCE units and one CCE includes 9 REGs.

The UE is set to confirm M (L) CCEs which are arranged consecutively oraccording to a specific rule in order to determine whether a PDCCHcomposed of L CCEs is transmitted to the UE. The value L considered whenthe UE receives the PDCCH may be plural. A set of CCEs which should beconfirmed when the UE receives the PDCCH is referred to as a PDCCHsearch space. For example, in the LTE system, the PDCCH search space isdefined as shown in Table 1.

TABLE 1 Search space S_(k) ^((L)) Aggregation Size Number of PDCCH Typelevel L [in CCEs] candidates M^((L)) DCI formats UE- 1 6 6 0, 1, 1A,specific 2 12 6 1B, 2 4 8 2 8 16 2 Common 4 16 4 0, 1A, 1C, 8 16 2 3/3A

In Table 1, CCE aggregation level (L) denotes the number of CCEsconfiguring the PDCCH, S^((L)) _(k)) denotes the PDCCH search space, andM^((L)) denotes the number of PDCCH candidates to be monitored in thesearch space.

The PDCCH search space may be divided into a UE-specific search space inwhich access is allowed for only a specific UE and a common search spacein which access is allowed for all UEs within a cell. The UE monitorsthe common search space at L=4 and 8 and monitors the UE-specific searchspace at L=1, 2, 4 and 8. The common search space and the UE-specificsearch space may overlap.

In addition, the location of a first CCE (having a smallest index) inthe PDCCH search space applied to a certain UE with respect to eachvalue L is changed according to the UEs for each subframe. This isreferred to as PDCCH search space hashing.

FIG. 7 shows an exemplary CCE distribution in a system band. Referringto FIG. 7, a plurality of CCEs which are logically consecutive is inputto an interleaver. The interleaver performs a function for interleavingthe plurality of CCEs in REG units. Accordingly, the REGs configuringthe CCE are scattered in the overall frequency/time domain within thecontrol region of the subframe. In conclusion, the control channel isconstructed in units of a CCE and interleaving is performed in units ofan REG, such that frequency diversity and interference randomizationgain can be maximized.

FIG. 8 illustrates an uplink (UL) subframe structure for use in an LTEsystem.

Referring to FIG. 6, the UL subframe may be classified into a firstregion to which a physical uplink control channel (PUCCH) carryingcontrol information is allocated and a second region to which a physicaluplink shared channel (PUSCH) carrying user data is allocated. Thecenter part of the subframe is allocated to PUSCH, and both parts of thedata region are allocated to PUCCH in the frequency domain Controlinformation transmitted over PUCCH may include ACK/NACK used in HARQ, aChannel Quality Indictor (CQI) indicating a downlink channel state, aRank Indicator (RI) for MIMO, a scheduling request (SR) acting as a ULresource allocation request, etc. PUCCH for one UE uses one resourceblock (RB) that occupies different frequencies in each slot of thesubframe. That is, two RBs allocated to PUCCH are frequency-hopped at aboundary between slots. In particular, as can be seen from FIG. 7, FIG.7 is a conceptual diagram illustrating a relay backhaul link and a relayaccess link for use in a wireless communication system. As can be seenfrom FIG. 7, PUCCH of m=0, PUCCH of m=1, PUCCH of m=2, and PUCCH of m=3are allocated to the subframe.

The present invention provides an efficient HARQ scheme for dynamicallychanging specific radio resources (for example, downlink resource oruplink resource) allocated from the eNB to the UE such that it isdetermined whether the specific radio resources will be used fordownlink or uplink according to traffic load variation.

First, prior to describing detailed description of the proposed schemes,uplink-downlink configuration defined in the 3GPP LTE—based TDD systemwill hereinafter be described in detail.

TABLE 2 Uplink- Downlink- downlink to-Uplink config- Switch-pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D DD D D 6 5 ms D S U U U D S U U D

In Table 1, D, U and S are allocated respective subframe numbers. Inmore detail, D denotes a downlink subframe, U denotes an uplinksubframe, and S denotes a switching point. In addition, the followingTable 3 shows an uplink subframe number (index) for controlling a UE totransmit uplink ACK/NACK of the corresponding downlink signal in the3GPP LTE system.

TABLE 3 UL-DL subframe number Configuration 0 1 2 3 4 5 6 7 8 9 0 4 7 —— — 9 2 — — — 1 7 7 — — 8 2 2 — — 3 2 7 7 — 7 2 2 2 — 2 7 3 4 2 — — — 22 3 3 4 4 2 2 — — 2 2 3 3 3 3 5 2 2 — 2 2 2 2 2 2 2 6 7 8 — — — 2 3 — —4

Specifically, in Table 3, ‘-’ indicates configuration of an uplinksubframe, and a number allocated to each subframe number indicates anuplink subframe index. That is, ‘-’ indicates an uplink subframe indexinterlocking with the corresponding downlink subframe.

In order to dynamically change the use of specific legacy radioresources, that is, in order to change a specific radio resource (forexample, UL resource or DL resource) allocated to the UE to anotherradio resource for the purpose of UL or DL purpose according to trafficload variation, additional UL/DL configuration may be indicated throughUE-specific dedicated RRC signaling (for example, subframereconfiguration message). Alternatively, the set of subframes changedfrom UL subframes to DL subframes and the set of subframes changed fromDL subframes to UL subframes may be simultaneously indicated, or the setof subframes changed from DL subframes to UL subframes may also beindicated. In addition, for the set of subframes changed from ULsubframes to DL subframes and the set of subframes changed from DLsubframes to UL subframes, additional UL/DL configurations havingindividual usages may also be indicated.

Alternatively, a specific field of control information transmittedthrough a physical control channel may be (re)used (or (re)interpreted)as an indicator, such that the usage of a specific subframe may bedynamically changed. For example, the specific field may be a CarrierIndication field (CIF), a Downlink Assignment Index (DAI) or a UL index.

In this case, the above-mentioned methods are representative examples ofthe method for dynamically changing the usage of specific radioresources, and may perform signaling of the subframe use variation usingother methods.

In addition, the eNB may inform the UE of (position) informationregarding the set of specific radio resources using a bitmap or thelike. The set of specific radio resources may dynamically change the useof radio resources through RRC signaling. Thereafter, the eNB may informthe UE of specific information as to whether the use of a specific radioresource set indicated through RRC signaling using a specific field (forexample, CIF or DAI, or UL index) of a control channel That is, the eNBmay also inform the UE of activation or deactivation of such changeusing the specific field of the control channel. For example, assumingthat the set of UL subframes designated through RRC signaling iscomposed of UL subframe #a and UL subframe #b, the eNB may inform the UEof specific information as to whether the use of the set of radioresources is changed using a specific field of a 1-bit sized controlchannel That is, if the specific field is set to 1, this means that ULsubframe #a and UL subframe #b are respectively changed to DL subframe#a and DL subframe #b. If the specific field is set to zero (0), thismeans that the subframe #a and the subframe #b are used for the purposeof uplink purpose for initialization.

Needless to say, specific information indicating whether the use ofindividual radio resources constructing the specific radio resource setis changed may be indicated through a specific field (for example, CIFor DAI, or UL index) of a control channel. For example, assuming thatthe set of UL subframes designated by RRC signaling is composed of ULsubframe #a and UL subframe #b, it may be possible to indicateinformation as to whether the use of an individual radio set is changedusing the 2-bit sized information. For example, if the specific field isset to 11, this means that the subframe #a and the subframe #b are usedas DL subframes. If the specific field is set to 10, this means that thesubframe #a is used as a DL subframe and the subframe #b is used as a ULsubframe. In addition, if the specific field is set to 01, this meansthat the subframe #a is used as the UL subframe and the subframe #b isused as the DL subframe. If the specific field is set to 00, this meansthat both the subframe #a and the subframe #b are used as UL subframesfor the purpose of initialization.

In addition, assuming that the UL grant is not received at SF #(n−4) inthe subframe (for example, SF #n), the usage of which can be dynamicallychanged (for example, the use of UL resource can be changed to DLcommunication use), if the UL grant is not received at SF #(n−4), blinddecoding (BD) is primarily performed at the corresponding subframe (forexample, SF #n), such that the specific field can be detected.

In addition, the eNB may inform the UE of the set of a plurality ofspecific radio resources (i.e., the set of candidates) through which theuse of legacy radio resources can be dynamically changed through RRCsignaling, and may also inform the UE of the set of radio resources towhich the use change is applied using a specific field of a controlchannel.

Although the following embodiments will assume the case of indicatingwhether a dynamic subframe is changed through UE-specific RRC signalingfor convenience of description, the other case of indicating whether adynamic subframe is changed can also be applied to the followingembodiments.

FIG. 9 shows an example for implementing a subframe dynamic changethrough dedicated RRC signaling in an LTE TDD system. Specifically,referring to FIG. 9, UE 1 and UE 2 are operated in UL/DL configuration#3, and UE 1 denotes a UE (i.e., Advanced-UE (A-UE)) for dynamicallychanging the use of a subframe. UE 2 denotes a UE (i.e., legacy UE) fordynamically maintaining UL/DL configuration allocated through a legacySIB (System Information Block) without change.

Referring to FIG. 9, assuming that UE 1 receives a subframereconfiguration message for indicating UL/DL configuration #4 at DLsubframe #9, this means that the use of a legacy subframe #4 isdynamically changed from uplink use to downlink use.

However, when the use of a specific radio resource is dynamicallychanged according to the above-mentioned scheme, it is impossible toguarantee the HARQ process of legacy UL/DL configuration without change.For example, according to the legacy UL/DL configuration #3, when aPHICH of UL subframe #4 is received as NACK at DL subframe #0, it isimpossible to retransmit UL subframe #4 as shown in FIG. 9, because theUL subframe #4 is changed to DL subframe #4. That is, it is impossiblefor the UL HARQ process linked to UL subframe #4 to be normallyoperated.

Accordingly, when the LTE TDD system uses a method for dynamicallychanging the use of a specific radio resource allocated from the eNB tothe UE, the present invention provides a method for efficientlysupporting the UL/DL HARQ operation.

First Embodiment

If the use of specific radio resources is dynamically changed usingdedicated RRC signaling (i.e., subframe reconfiguration message), the UEstarts operation from a reception time (SF #n) of the subframereconfiguration message indicating UL/DL configuration #x, and thenterminates the UL HARQ processes based on the legacy UL/DL configuration(for example, UL/DL configuration #y) incapable of guaranteeing the ULHARQ timeline using the UL/DL configuration #x.

For example, from among UL HARQ processes based on the legacy UL/DLconfiguration #y, UL HARQ processes associated with the legacy ULsubframe #a, the use of which is dynamically changed by the UL/DLconfiguration #x, are terminated. For example, the legacy UL subframe #ais changed to DL subframe #a. In this case, the UE may assume thatsuccessful UL data (i.e., ACK) transmission of the terminated UL HARQprocesses based on UL/DL configuration #y has been achieved, and maythen report the ACK to a higher layer. For convenience of description,all UL HARQ processes instead of individual UL HARQ processes may alsobe terminated as necessary.

The termination operation may refer to the UE operation in which a PHICH(i.e., SF #m (where, m<n)) received before a reception time (SF #n) or aPHICH (i.e., SF #k (where, n≤k)) to be received after the reception time(SF #n) at which the UE receives a subframe reconfiguration message maynot be considered as ACK or may not be decoded, such that the PHICH maybe considered as ACK at all times.

In accordance with another scheme for terminating UL HARQ processes, theeNB may transmit a PHICH of the terminated UL HARQ processes to the UE.

In addition, a specific time point (SF #p) to which the additionallyallocated UL/DL configuration #a and associated UL HARQ operations areactually applied may include a reception time (SF #n) at which the UEreceives the subframe reconfiguration message, and begins with a firstSF (SF #k) (of the first SFN) located after a specific time at which asubframe pattern length (or period) of the legacy UL/DL configuration #yis completed after SF #n. For example, assuming that the UE receives asubframe reconfiguration message indicating UL/DL configuration #4 at DLsubframe #7 under the same situation as in FIG. 9, the additionallyallocated UL/DL configuration #4 and associated HARQ process operationare actually applied to subframes starting from the nearest DL subframe#0 located after DL subframe #7.

FIG. 10 shows an example of using an uplink HARQ operation according toa first embodiment.

Referring to FIG. 10, when the subframe reconfiguration messageindicating UL/DL configuration #4 is received at DL subframe #8, the ULHARQ timeline regarding the legacy UL/DL configuration #3—based ULsubframe #4 cannot be guaranteed using the additionally allocated UL/DLconfiguration #4, such that the associated HARQ process is terminated.

In this case, the UE does not implicitly decode a PHICH (i.e., DLsubframe #0) of the UL subframe #4 based on the legacy UL/DLconfiguration #3, and always considers the PHICH to be ACK. In addition,a specific time at which the additionally allocated UL/DL configuration#4 is actually applied may start from the nearest DL subframe #0 locatedafter DL subframe #8 according to the above-mentioned scheme.

Second Embodiment

(1) When the use of specific radio resource having been allocated isdynamically changed, after a subframe reconfiguration message indicatingUL/DL configuration #x is received at SF #n, the UL/DL configuration #xand a specific time (SF #p) at which the UL HARQ process operation isapplied may correspond to a first subframe located after a terminationtime point of “repetition period of a UL subframe pattern used by one ULHARQ process” of the legacy UL/DL configuration #y. For convenience ofdescription, “repetition period of the UL subframe pattern used by oneUL HARQ process” is referred to as a repetition period.

For reference, the repetition period under the 3GPP LTE TDD systemenvironment may be set to 70 ms at UL/DL configuration #0, 60 ms atUL/DL configuration #6, and 10 ms at UL/DL configuration #1, #2, #3, #4,or #5. Specifically, in the case of UL/DL configuration #0, the ULsubframe pattern used by one UL HARQ process may include UL subframe #2for initial UL transmission, and is repeated in the order of UL subframe#3→UL subframe #4→UL subframe #7→UL subframe #8→UL subframe #9→ULsubframe #2. In this case, the repetition period is the sum of intervalsamong individual UL subframes, and is denoted by 70 ms(=11+11+13+11+11+13).

In accordance with another scheme, a specific time at which theadditionally allocated UL/DL configuration #a and associated UL HARQoperations are actually applied may be denoted by a specific period Tseparately from the repetition period of the legacy UL/DL configuration#y. In this case, the above-mentioned repetition period may be repeatedwith a predetermined start time (for example, subframe #0 of a radioframe index #0).

After the repetition period or a separate specific period T isrepeatedly applied on the assumption that the legacy UL/DL configuration#y is applied to radio frames starting from a radio frame of SFN=0, astart point (or reference point) of the above repetition period or theseparate specific period T includes a specific time SF #n at which thesubframe reconfiguration message is received, and may be set to a firstsubframe of a radio frame having the nearest first SFN located after thelapse of a time at which the repetition period or separate specificperiod T is completed. In this case, the SFN has an yone of integervalues from 0 to 1023, 1024 radio frames have a length of 10240 ms, andthe SFN is repeated at intervals of the length 10240 ms.

For example, on the assumption that the UE receives the subframereconfiguration message indicating UL/DL configuration #4 at DL subframe#6 under the same situation as in FIG. 9, a start point of therepetition period of the legacy UL/DL configuration #3 according to theabove-mentioned method is set to DL subframe #0 located at the nearestposition before the position of DL subframe #6. Therefore, a specifictime at which the additionally allocated DL/UL configuration #4 andassociated UL HARQ process operation are applied is set to DL subframe#0 located at the nearest position after the position of DL subframe #6.

FIG. 11 shows an example of using an uplink HARQ operation according toa second embodiment. Specifically, the subframe reconfiguration messageis received at DL subframe #5 as shown in FIG. 11, differently from FIG.10.

Referring to FIG. 11, the repetition period of the legacy UL/DLconfiguration #3 is set to 10 ms, and a completion time of thecorresponding repetition period according to the above scheme is set to#9. Therefore, although the subframe reconfiguration message indicatingUL/DL configuration #4 is received at DL subframe #5, a specific time atwhich the additionally allocated UL/DL configuration #4 and associatedUL HARQ process operation are applied may be set to DL subframe #0located at the nearest position after the position of DL subframe #5.

In addition, it is impossible to guarantee a UL HARQ timeline of ULsubframe #4 based on the legacy UL/DL configuration #3 using theadditionally allocated UL/DL configuration #4, and the uplink HARQprocess is terminated according to the proposed scheme. In this case,the UE does not implicitly decode a PHICH (i.e., DL subframe #0) of ULsubframe #4 based on the legacy UL/DL configuration #3, and alwaysconsiders the PHICH as an ACK.

(2) In another scheme, in order to allow the eNB to inform the UE of aspecific time (SF #p) at which the additionally allocated UL/DLconfiguration #x and associated UL HARQ process operation are applied,the eNB may inform the UE of additional signaling information includingnot only a subframe reconfiguration message indicating UL/DLconfiguration #x but also activation time (G) information through higherlayer signaling. In this case, the UE, that has received the additionalsignaling information including the subframe reconfiguration message andthe activation time (G) information at SF #n, may apply the additionallyallocated UL/DL configuration #x and associated UL HARQ processoperation at a time starting from SF #(n+G+1).

For example, assuming that the UE receives additional higher layersignaling including not only a subframe reconfiguration messageindicating UL/DL configuration #4 but also the activation time G of 3 atDL subframe #6 under the same situation of FIG. 9, a specific time(located at the nearest position after DL subframe #6) to which UL/DLconfiguration #4 and associated UL HARQ process are actually applied maystart from DL subframe #0.

On the contrary, according to a second embodiment, after completion ofthe legacy UL/DL configuration #y—based UL HARQ processes incapable ofguaranteeing UL HARQ timeline using the additionally allocated UL/DLconfiguration #x, a new HARQ process operation can be carried out.

For example, UL HARQ processes associated with the subframe #a (forexample, legacy UL subframe #a is changed to DL subframe #a), the use ofwhich is changed from uplink to downlink by UL/DL configuration #x fromamong the legacy UL/DL configuration #y—based UL HARQ processes, areterminated. In this case, the UE assumes that UL data (i.e., ACK) issuccessfully transmitted in association with the terminated UL HARQprocesses based on UL/DL configuration #y, such that it may report theACK to a higher layer. Alternatively, for convenience of description,the above operations are not terminated per UL HARQ process, and all ULHARQ processes may be terminated.

The termination operation may refer to the UE operation in which a PHICH(i.e., SF #i (where, i<p)) received before a first SF (SF #p) or a PHICH(i.e., SF #i (where, p≤j)) to be received after the first SF (SF #p) atwhich a repetition period of the legacy UL/DL configuration #y or aseparately-established specific period T is completed, may not beconsidered as ACK or may not be decoded, such that the PHICH may beconsidered ACK at all times.

In addition, in accordance with still another scheme in which the legacyUL/DL configuration #y—based UL HARQ processes incapable of guaranteeingUL HARQ timeline using UL/DL configuration #x are terminated, the eNBmay transmit a PHICH regarding the corresponding terminated UL HARQprocesses as ACK.

In accordance with the above-mentioned first and second embodiments, theUE may always consider a PHICH of the terminated UL HARQ processes asACK. Therefore, a PHICH of the legacy UL/DL configuration #y—based ULHARQ processes incapable of guaranteeing UL HARQ timeline may not beimplicitly decoded using UL/DL configuration #x being additionallyallocated by the subframe reconfiguration message.

In addition, the eNB may inform the UE of not only additional 1-bit RRCsignaling information for activating or deactivating a PHICH decodingoperation (of the terminated UL HARQ processes) but also the subframereconfiguration message, or may independently inform the UE of each ofthe additional 1-bit RRC signaling information and the subframereconfiguration message, such that the same operation can be implementedby the eNB and the UE. In this case, the UE may limit the applicationrange of PHICH decoding deactivation or activation signaling receivedfrom the eNB through RRC signaling to the terminated UL HARQ processesbased on the legacy UL/DL configuration #y. For example, the UE havingreceived PHICH decoding deactivation signaling considers successful ULdata transmission, and may perform UL retransmission according towhether a New Data Indication (NDI) value contained in DL controlinformation is toggled.

Third Embodiment

In accordance with the third embodiment, in order to dynamically changethe use of specific conventionally allocated radio resources, the eNBmay inform the UE of a subframe pattern (i.e., UL/DL configurationcombination) composed of N UL/DL subframe configurations (where N≥1 orN>1) through dedicated RRC signaling (i.e., a subframe reconfigurationmessage), and the UE having received the above information is operatedby repeated application of the UL/DL subframe configuration combination.In this case, the UE and eNB may (implicitly) assume that the length(i.e., a pattern length (T_p)) of UL/DL configuration combination isdenoted by 10*N (ms).

FIG. 12 shows an example for dynamically changing UL/DL configurationaccording to a third embodiment. For convenience of description, thelegacy UL/DL configuration #y of FIG. 12 is denoted by C.

Referring to FIG. 12, the eNB may inform the UE of UL/DL configurationcombination (AAABBB) composed of 6 UL/DL configurations through areconfiguration message (based on higher layer signaling), and the UEhaving received the above information is operated by implicitlyrepeating the UL/DL configuration combination (AAABBB) at intervals of60 ms.

In another scheme, the eNB may explicitly inform the UE of the UL/DLconfiguration combination and the pattern length (T_p) thereof throughdedicated RRC signaling. For example, the eNB may inform the UE ofinformation on the pattern length (T_p) of the UL/DL configurationcombination. In this case, the pattern length (T_p) is divided by 10,and the divided value is converted into a binary value. The UE havingthe above information may consider the resultant value to be the patternlength (T_p) of the UL/DL configuration combination. In this case, ifthe corresponding information is converted into a decimal number and thedecimal number is multiplied by 10, the resultant value can be obtained.

A specific time (SF #p) to which a UL/DL configuration combination andassociated UL HARQ process operation are applied may include a specifictime (SF #n) at which the subframe reconfiguration message is received,after the UL/DL configuration combination starting from the radio frameof SFN=0 is repeated applied during the time (T_p), and may begin with afirst subframe of a radio frame having a first SFN located after theearliest time at which T_p is completed.

In accordance with another scheme, a specific time (SF #9) at which aUL/DL configuration combination and associated UL HARQ process operationare applied may include a time (SF #n) at which the subframereconfiguration message is received, after the legacy UL/DLconfiguration #y is repeatedly applied to radio frames starting from aradio frame of SFN=0 on the basis of the repetition period or(predetermined) specific period T, and may begin with a first subframeof a radio frame having a first SFN located after the earliest time atwhich the repetition period or (predefined) specific period T iscompleted.

In accordance with another scheme, a specific time (SF #p) to whichUL/DL configuration combination and associated UL HARQ processoperations are applied, may include a specific time (SF #n) at which thesubframe reconfiguration message is received, and may begin with a firstsubframe #k (of a radio frame having a first SFN) located after theearliest time at which the SF pattern period (for example, 10 ms) of thelegacy UL/DL configuration #y is completed. For example, assuming thatthe UE receives the subframe reconfiguration message at DL subframe #8under the same situation as in FIG. 9, a specific time at which UL/DLconfiguration combination and associated UL HARQ process operation areapplied may start from DL subframe #0 located at the nearest positionlocated after the position of the DL subframe #8.

In addition, in order to allow the eNB to inform the UE of a specifictime (SF #p) at which the UL/DL configuration combination and associatedUL HARQ process operation are applied, the eNB may inform the UE ofadditional signaling information including not only UL/DL configurationinformation but also activation time (G) information through higherlayer signaling. In this case, the UE, that has received the additionalsignaling information including UL/DL configuration information andactivation time (G) information at SF #n, may apply the additionallyallocated UL/DL configuration #x and associated UL HARQ processoperation at a time starting from SF #(n+G+1).

For example, assuming that the UE receives additional higher layersignaling including not only UL/DL configuration combination but alsothe activation time of G=1 at DL subframe #8 under the same situation ofFIG. 9, a specific time (located at the nearest position after DLsubframe #8) to which the UL/DL configuration combination and associatedUL HARQ process are actually applied may start from DL subframe #0.

In addition, if a current combination is changed to UL/DL configurationcombination at the legacy UL/DL configuration #y, or if UL/DLconfiguration change occurs within the UL/DL configuration combination,the legacy UL/DL configuration—based UL HARQ processes incapable ofguaranteeing UL HARQ timeline are terminated using the changed UL/DLconfiguration. In this case, the UE may assume that successful UL data(i.e., ACK) transmission of the terminated UL HARQ processes based onUL/DL configuration has been achieved, and may then report the ACK to ahigher layer. For convenience of description, all UL HARQ processesinstead of individual UL HARQ processes may also be terminated asnecessary.

In the same manner as in the first and second embodiments, on the basisof a specific time (SF #p) at which the changed UL/DL configuration andassociated UL HARQ process are actually applied, or on the basis ofanother specific time (SF #n) at which the subframe reconfigurationmessage is received, the termination operation may consider a PHICH(i.e., SF #i, where i<p or i<n) received before the above specific timeor a PHICH (i.e., SF #j, where p≤j or n≤j)) to be received after theabove specific time as an ACK or may not decode the PHICH, and mayalways consider the PHICH to be the ACK. Specifically, the terminationoperation performed when the UL/DL configuration change occurs withinUL/DL configuration combination may not consider a PHICH (i.e., SF #i,where i<received before a specific time at which UL/DL configurationchange occurs, or a PHICH (i.e., SF #j, where f≤j) to be received afterthe specific time to be an ACK, or may not decode the PHICH, and mayalways consider the PHICH to be the ACK.

In this way, a third embodiment may also control the eNB to transmit aPHICH of the corresponding terminated UL HARQ process as an ACKaccording to another scheme in which the legacy UL/DLconfiguration—based UL HARQ processes incapable of guaranteeing the ULHARQ timeline are terminated using the changed UL/DL configuration.

Fourth Embodiment

In accordance with the fourth embodiment, when the use of a specificradio resource allocated from the eNB to the UE is dynamically changedin the TDD system, the fourth embodiment proposes a method forcontrolling the UE to efficiently transmit UL ACK/NACK. That is, thefourth embodiment proposes a UL ACK/NACK transmission timeline. Forconvenience of description, the legacy UL/DL configuration is defined asUL/DL configuration #y, and UL/DL configuration additionally allocatedby the subframe reconfiguration message is defined as UL/DLconfiguration #x.

In addition, the following UL ACK/NACK transmission timeline can beapplied to all of the above-mentioned embodiments, and may be sharedwith higher layer signaling or the like before the above-mentionedembodiments are applied between the eNB and the UE. Alternatively, theUL ACK/NACK transmission timeline may be implicitly recognized betweenthe eNB and the UE according to application or non-application of theabove-mentioned embodiments.

A-1) If UL SF #n acting as a UL resource is changed to a DL resource(for example, DL SF #n), UL ACK/NACK of the legacy (UL/DL configurationbased) DL resources interlocked to transmit the UL ACK/NACK through ULSF #n may be transmitted at the nearest available UL SF satisfying UL SF#(n+p) (where, p≥1, p is an integer).

In this case, “available UL SF” may denote i) a UL SF to be used fortransmission of the legacy UL ACK/NACK transmission, or may denote ii)all UL SFs configured by UL-DL configuration.

A-2) In addition, from among UL subframes #i (where i<z) located beforea specific time (SF #z) at which the additionally allocated UL/DLconfiguration #x and associated UL HARQ process operation are actuallyapplied, UL ACK/NACK of the remaining DL subframes other than DLsubframes interlocked with UL SF #n of the above case A-1 may be basedon UL ACK/NACK timeline of the legacy UL/DL configuration #y. Inaddition, UL ACK/NACK of DL subframe #j (where j≥z) located after aspecific time (SF #z) at which UL/DL configuration #x and associated ULHARQ process operation are actually applied may be based on UL ACK/NACKof UL/DL configuration #x.

A-3) UL ACK/NACK of DL subframes interlocked to transmit UL ACK/NACKthrough UL subframe #h (where h≥z) located after a specific time (SF #z)to which the additionally allocated UL/DL configuration #x andassociated UL HARQ process operation are actually applied may be basedon UL ACK/NACK timeline of UL/DL configuration #x. In this case, DLsubframes may include DL subframes interlocked with UL SF #n of theabove case A-1. Furthermore, UL ACK/NACK of DL subframes interlocked totransmit UL ACK/NACK through UL subframe #t (where t<z) located before aspecific time (SF #z) to which UL/DL configuration #x and associated ULHARQ process operation are actually applied may be based on UL ACK/NACKtimeline of the legacy UL/DL configuration #y. In another scheme, DLsubframes interlocked with UL SF #n may be limited to exceptionallysatisfy the above scheme A-1 as necessary.

B-1) If UL resource (i.e., UL subframe #n) is changed to DL resource(i.e., DL subframe #n), UL ACK/NACK of DL subframe #n may be transmittedthrough (the nearest) available UL SF satisfying UL subframe #(n+k)(where k≥4, k is an integer). Likewise, “available UL SF” may denote i)a UL SF to be used for legacy UL ACK/NACK transmission, or may denoteii) all UL SFs configured by UL-DL configuration.

B-2) Alternatively, UL ACK/NACK of DL subframe #n (generated by thechanged use of UL subframe #n) may also follow UL ACK/NACK timeline ofthe additionally allocated UL/DL configuration #x.

C) If UL resource (i.e., UL subframe #n) is changed to DL resource(i.e., DL subframe #n), UL ACK/NACK of DL subframe #n may be configuredto satisfy UL ACK/NACK transmission timing of UL-DL configurationsatisfying all or some of the following specific conditions within thescope of a total candidate aggregation (i.e., UL/DL configurations #0˜#6of Table 2) capable of being designated by UL/DL configuration.

In this case, examples of the specific condition may be configured tosatisfy UL ACK/NACK timeline of the following UL-DL configurations (1),(2), and (3). In more detail, the UL-DL configuration (1) is a UL-DLconfiguration in which the corresponding UL SF #n is allocated as DL SF#n. The UL-DL configuration (2) is a UL-DL configuration forguaranteeing the fastest UL ACK/NACK transmission timeline satisfying ULsubframe #m (where, m≥(n+4)), and the UL-DL configuration (3) allowscandidate UL subframes configured by UL subframe #m (where, m≥(n+4)) tosatisfy conditions limited to a subset of the UL subframe set allocatedby UL/DL configuration #x.

In addition, according to the above-mentioned scheme (C), if UL resource(i.e., UL subframe #n) is changed to DL resource (i.e., DL subframe #n),the scheme (C) may be used to establish each (or all) UL ACK/NACKtimeline(s) of the legacy UL/DL configuration #y—based DL subframesinterlocked to transmit UL ACK/NACK through UL subframe #n.

Fifth Embodiment

X) UL/DL configuration #x additionally allocated through dedicated RRCsignaling (i.e., subframe reconfiguration message) may be used for onepurpose for dynamically changing the use of specific radio resources ofthe legacy UL/DL configuration #y designated as SIB, or may also be usedfor the other purpose (for example, measurement purpose such as RSRQ,RSRP or RLM, or HARQ timeline) of the legacy UL/DL configuration #y.

For example, only a specific part from among the HARQ operation of UL/DLconfiguration #y designated as SIB may be operated according to UL/DLconfiguration #x different from that of the HARQ timeline defined in thelegacy UL/DL configuration #y. That is, all or some parts of therelationship between a reception time of a UL grant and PHICH of thelegacy UL/DL configuration #y and a PUSCH transmission time, therelationship between a PUSCH transmission time and a PHICH reading time,and the relationship between a PDSCH reception time and a UL ACK/NACKtransmission time may be operated according to the additionallyallocated UL/DL configuration #x.

In another scheme, the above operation may be achieved according to onlyUL-DL configuration #y designated as legacy SIB for measurement usagesuch as RSRQ, RSRP, or RLM. For example, the measurement process may beperformed only under a DL SF based on the legacy UL-DL configuration #y.In another example, during the measurement process, a common DL subframebetween the legacy UL/DL configuration #y (designated as SIB) and theadditionally allocated UL/DL configuration #x may be used as necessary.

Y) In another example, when individual component carriers (CCs) areconfigured to use different UL/DL configurations under the carrieraggregation (CA) environment and cross carrier scheduling (CCS) of asecondary component carrier (SCell) is performed at PCell, the UL/DLconfiguration #x additionally allocated through dedicated RRC signalingmay be used for a specific purpose only (for example, measurement suchas RSRQ, RSRP, or RLM, or HARQ timeline) from among the legacy UL/DLconfiguration operation per CC.

That is, only a specific part of the HARQ operation of the legacy per-CCUL/DL configuration may satisfy the HARQ timeline defined in the legacyper-CC UL/DL configuration and other UL/DL configuration #x. Forexample, all or some parts of the relationship between a reception timeof UL grant and PHICH of the legacy per-CC UL/DL configuration and aPUSCH transmission time, the relationship between a PUSCH transmissiontime and a PHICH reading time, and the relationship between a PDSCHreception time and a UL ACK/NACK transmission time may be operatedaccording to the additionally allocated UL/DL configuration #x.

In addition, a total number of additionally allocated UL/DLconfigurations #x may be set to 1 (that is, if all component carriersuse a single specific common UL/DL configuration that is additionallyallocated), may be set to a total number of secondary component carriers(that is, if SCell separately uses different UL/DL configurations havingbeen allocated several times corresponding to a total number of SCellsthrough dedicated RRC signaling), or may also be set to a total numberof component carriers (that is, if all component carriers individuallyuse different UL/DL configurations having been allocated several timescorresponding to a total number of component carriers through dedicatedRRC signaling).

Sixth Embodiment

The sixth embodiment provides an ACK/NACK transmission method forcontrolling a UE to efficiently transmit UL ACK/NACK when the use ofspecific radio resources allocated from the eNB to the UE is dynamicallychanged in the TDD system. For convenience of description in thefollowing, the legacy UL/DL configuration is defined as UL/DLconfiguration #y, and UL/DL configuration additionally allocated by thesubframe reconfiguration message is defined as UL/DL configuration #x.Likewise, the following ACK/NACK transmission method of the UE can beapplied to all of the above-mentioned embodiments.

If a specific radio resource is dynamically changed for DL or ULpurpose, the UE may implicitly change the legacy ACK/NACK transmissionscheme notified through a higher layer according to a variation of thenumber of DL subframes interlocked with UL subframe. As a result, beforea specific time (SF #z) at which the additionally allocated UL/DLconfiguration #x is actually applied, UL ACK/NACK transmission of a DLsubframe operated by UL ACK/NACK timeline based on another UL/DLconfiguration but not UL ACK/NACK timeline of UL/DL configuration #x canbe guaranteed.

For example, when UL subframe #n is changed to DL subframe #n, ULACK/NACK transmission of the legacy UL/DL configuration #y—based DLsubframes interlocked to transmit UL ACK/NACK through UL subframe #n canbe guaranteed. In this case, the changed ACK/NACK transmission schememay be applied only to UL subframe #g of a specific time for which thechanged ACK/NACK transmission scheme is needed, may always be applied toACK/NACK transmission at a subsequent UL subframe #m (where m≥g)including UL subframe #g. In addition, the UE may first follow thelegacy ACK/NACK transmission scheme within the range of a maximum numberof DL subframes interlocked with UL subframes supporting the legacyACK/NACK transmission scheme.

In more detail, the eNB may recognize whether the UE will be operatedaccording to the legacy ACK/NACK transmission scheme or other schemes,on the basis of “used or non-used state” and “application position” ofthe above-mentioned embodiments. In this case, the used change rule maybe exemplarily defined as “PUCCH format 1a/1b→channel selectionscheme→PUCCH format 3”, “PUCCH format 1a/1b→channel selectionscheme→ACK/NACK bundling”, or “PUCCH format 1a/1b→channel selectionscheme or ACK/NACK bundling or PUCCH format 3”.

In this case, since ACK/NACK resources of PUCCH format 3 are decidedthrough higher layer signaling, the eNB may preallocate the ACK/NACKresource for PUCCH format 3 to the UE on the condition that there is ahigh probability of employing PUCCH format 3 when the above proposedschemes are applied under a specific UL-DL configuration.

In accordance with the rule for changing the ACK/NACK transmissionscheme to be used by UE, rules for changing multiple ACK/NACKtransmission schemes may be pre-configured and shared between the eNBand the UE before the above-mentioned embodiments are used, and the eNBmay inform the UE of signaling information of bit informationcorresponding to a specific rule through higher layer signaling.Alternatively, after only one rule of changing the ACK/NACK transmissionscheme is shared between the eNB and the UE, the eNB may inform the UEof higher layer signaling activating this rule. Alternatively, after onerule is shared between the eNB and the UE, the eNB may inform the UE ofhigher layer signaling (for example, 1-bit higher layer signaling) foractivating this rule.

Alternatively, the above-mentioned scheme may be changed only to onespecific ACK/NACK transmission scheme under the condition that thelegacy ACK/NACK transmission scheme must be changed. For example, PUCCHformat 3 is established according to one specific ACK/NACK transmissionscheme, and the eNB may inform the UE of the corresponding ACK/NACKresources through higher layer signaling.

Seventh Embodiment

A specific subframe (for example, SF #e) may be used as a UL subframe inthe legacy UL/DL configuration #y designated by SIB, and may be used asa DL subframe on the additionally allocated UL/DL configuration #x. Inthis case, although the corresponding SF #e is used as a DL subframeaccording to UL/DL configuration #x, a control channel such as PDCCH maynot be transmitted at SF #e.

In this case, the eNB may perform PDSCH mapping starting from a firstsymbol at SF #e at which a control channel such as PDCCH is nottransmitted, or the eNB may pre-inform the UE of the position of aspecific start symbol through higher layer signaling or a predeterminedscheme, such that the eNB may perform PDSCH mapping. In addition,similar to a start symbol associated with PDSCH mapping, if the positionof a mapping termination symbol of PDSCH is ended before the last symbol(for example, it may be impossible for the last symbol to be used forthe purpose of Tx-Rx switching of the eNB or UE or for the (aperiodic orperiodic) SRS transmission purpose of the UE), the position of thetermination symbol may be shared between the eNB and the UE throughhigher layer signaling (or physical layer signaling) or thepredetermined scheme.

In addition, assuming that UL subframe #n is changed to DL subframe #n,all CRSs (for example, CRS located in both the control region and thedata region) may not be transmitted within DL subframe #n, or CRS (forexample, CRS located only in data (or control) region) of a specificregion may not be transmitted. Alternatively, PDCCH may not betransmitted from the eNB. In another scheme, assuming that UL subframe#n is changed to DL subframe #n, a specific rule in which DL subframe #nis operated as an MBSFN subframe may be shared and established betweenthe eNB and the UE. In still another scheme, assuming that UL subframe#n is changed to DL subframe #n, the eNB may inform the UE of specificinformation indicating that DL subframe #n is operated as an MBSFNsubframe through additional signaling (i.e., a specific field (e.g., CIFor DAI, or UL index) of a physical control channel or higher layersignaling). The above characteristics can be applied to theabove-mentioned embodiments.

In addition, assuming that UL subframe #n is changed to DL subframe #n,the last one or more symbols of the corresponding DL subframe #n may notbe used for PDSCH transmission. For example, the purpose of Tx-Rxswitching between the eNB and the UE or the (aperiodic or periodic) SRStransmission purpose of a UE may be used as an example. In addition,before UL subframe #n is changed to DL subframe #n, the UL subframe #nmay be set to UL subframe contained in cell-specific SRS (or UE-specificSRS) configuration information. In this case, the number (or theposition of mapping termination symbol) of symbols incapable of beingused for PDSCH information mapping from among symbols of DL subframe #nmay be shared (in advance) between the eNB and the UE through eitherhigher layer signaling (or physical layer signaling) or thepredetermined scheme.

In accordance with the above-mentioned embodiments, the eNB may informthe UE of additional UL/DL configuration #x through dedicated RRCsignaling, such that the eNB may decide a predetermined rule in a mannerthat the eNB can be used only for a specific purpose (for example,measurement purpose such as RSRQ, RSRP or RLM, or HARQ timeline) of theoperation of legacy UL/DL configuration #y designated as SIB.

For example, only a specific part from among the HARQ operation of UL/DLconfiguration #y designated as SIB may be operated according to UL/DLconfiguration #x different from that of the HARQ timeline defined in thelegacy UL/DL configuration #y. That is, all or some parts of therelationship between a reception time of a UL grant and PHICH of thelegacy UL/DL configuration #y and a PUSCH transmission time, therelationship between a PUSCH transmission time and a PHICH reading time,and the relationship between a PDSCH reception time and a UL ACK/NACKtransmission time may be operated according to the additionallyallocated UL/DL configuration #x.

The above-mentioned embodiments may be used for UEs located at a celledge receiving interference under the condition that UL/DL configurationbetween contiguous cells is different. In addition, the concept of thepresent invention may be extended to the carrier aggregation (CA) scheme(i.e., in-band CA scheme or out-band CA scheme).

The concept of the present invention can be extended to the case inwhich carrier aggregation (CA) is applied. For example, the aboveconcept of the present invention can also be applied to the case inwhich a specific CC may be commonly applied to a plurality of cells andthe usage of the corresponding CC is independently established per cell.In addition, the above embodiments can also be applied to the case inwhich the usage of a specific legacy radio resource of a Secondary CC(SCC) is changed to another usage using Cross Carrier Scheduling (CCS)at a Primary CC (PCC).

The concept of the present invention can also be extended to the case inwhich PDCCH or E-PDCCH based communication is performed. In addition,assuming that the extension carrier is used for additionalcommunication, the concept of the present invention can be applied tothe case in which the usage of radio resources of the correspondingextension carrier is established, and can also be applied to the othercase in which the inter-cell interference reduction coordinatedoperation is designed to share the extension carrier.

If it is impossible to perform UL/DL communication at a position of aspecific resource (time/frequency) for various reasons, the concept ofthe present invention can be extended to a method for solving the HARQ(or CSI reporting) problem. For example, assuming that an Almost BlankSubframe (ABS) is used to solve the inter-cell interference problemencountered in communication between the receiver and the transmitter,if UL-DL configurations of respective component carriers (CCs) used forcommunication between the transmitter and the receiver are differentfrom each other, and if ABS configurations of respective CCs used forcommunication between the receiver and the transmitter are differentfrom each other, the above-mentioned embodiments can be applied to thecase in which (time/frequency) resources valid for communication betweenthe receiver and the transmitter are not established (more specifically,in the case of communication between the eNB and the relay node, orcommunication between the relay node and the UE), or can also be appliedto the other case in which the usage of (predefined) specific resourceof each CC used for communication between the receiver and thetransmitter is (dynamically) changed according to a system load state.

The proposed schemes may perform D2D (Device-to-Device) communication ata specific band allocated for communication usage under the D2Dcommunication environment, or may change the usage of (cell) specificpredefined radio resource such that the above schemes can be extended tothe case of reusing D2D communication.

FIG. 13 is a block diagram illustrating a communication device accordingto embodiments of the present invention.

In FIG. 13, the communication device 1300 includes a processor 1310, amemory 1320, a Radio Frequency (RF) module 1330, a display module 1340,and a user interface (UI) module 1350.

The communication device 1300 is disclosed for illustrative purposesonly and certain modules may also be omitted from the communicationdevice 1300 as necessary. In addition, the communication device 1300 mayfurther include necessary modules. Some modules of the communicationdevice 1300 may be identified as more detailed modules. The processor1310 is configured to carry out the operations of the embodiments of thepresent invention. For detailed operations of the processor 1310reference may be made to FIGS. 1 to 12.

The memory 1320 is connected to the processor 1310, and stores anoperating system, applications, program code, data and the like. The RFmodule 1330 is connected to the processor 1310 and converts a basebandsignal into a radio frequency (RF) signal, or converts the RF signalinto the baseband signal. For these operations, the RF module 1330performs analog conversion, amplification, filtering, and frequencyup-conversion in order or performs such operations in reverse order. Thedisplay module 1340 is connected to the processor 1310 and displays avariety of information. The scope or spirit of the display module 1340of the present invention is not limited thereto, and the display module1340 may be any of well-known elements, for example, a Liquid CrystalDisplay (LCD), a Light Emitting Diode (LED), an Organic Light EmittingDiode (OLED) and the like. The user interface (UI) module 1350 isconnected to the processor 1310, and may be implemented as a combinationof user interfaces such as a keypad, a touchscreen, etc.

It will be appreciated by persons skilled in the art that the objectsthat can be achieved by the present invention are not limited to whathas been particularly described hereinabove and the above and otherobjects that the present invention can achieve will be more clearlyunderstood from the foregoing detailed description taken in conjunctionwith the accompanying drawings. The exemplary embodiments describedhereinabove are combinations of elements and features of the presentinvention. The elements or features may be considered selective unlessotherwise mentioned. Each element or feature may be practiced withoutbeing combined with other elements or features. Further, the embodimentsof the present invention may be constructed by combining parts of theelements and/or features. Operation orders described in the embodimentsof the present invention may be rearranged. Some constructions orcharacteristics of any one embodiment may be included in anotherembodiment and may be replaced with corresponding constructions orcharacteristics of another embodiment. It is apparent that the presentinvention may be embodied by a combination of claims which do not havean explicitly cited relation in the appended claims or may include newclaims by amendment after application.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the embodiments of the presentinvention may be implemented by one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, etc.

In a firmware or software configuration, the embodiments of the presentinvention may be achieved by a module, a procedure, a function, etc.performing the above-described functions or operations. Software codemay be stored in a memory unit and driven by a processor. The memoryunit is located at the interior or exterior of the processor and maytransmit data to and receive data from the processor via various knownmeans.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Therefore,the above-mentioned detailed description must be considered only forillustrative purposes instead of restrictive purposes. The scope of thepresent invention must be decided by a rational analysis of the claims,and all modifications within equivalent ranges of the present inventionare within the scope of the present invention.

INDUSTRIAL APPLICABILITY

As is apparent from the above description, although the retransmissionmethod and apparatus for configuring a dynamic subframe in a wirelesscommunication system have been disclosed on the basis of application to3GPP LTE, the inventive concept of the present invention is applicablenot only to 3GPP LTE, but also to other mobile communication systems.

The invention claimed is:
 1. A method for performing a hybrid automaticrepeat request-acknowledgement (HARQ-ACK) procedure by a user equipmentin a wireless communication system, the method comprising: receivingsystem information including a first TDD (Time Division Duplex)uplink-downlink configuration; receiving a TDD configuration, via RRC(Radio Resource Control) signaling, that comprises a second TDDuplink-downlink configuration and a HARQ reference configuration;reconfiguring an uplink-downlink configuration from the first TDDuplink-downlink configuration to the second TDD uplink-downlinkconfiguration; receiving downlink data in the reconfigureduplink-downlink configuration; and transmitting a HARQ-ACK/NACK(HARQ-ACK/Negative-ACK) related to the downlink data in the reconfigureduplink-downlink configuration based on the first TDD uplink-downlinkconfiguration and the HARQ reference configuration.
 2. The method ofclaim 1 further comprising: receiving a reconfiguration command, whereinreconfiguring the uplink-downlink configuration from the first TDDuplink-downlink configuration to the second TDD uplink-downlinkconfiguration is triggered by the receipt of the reconfigurationcommand.
 3. The method according to claim 2, wherein the reconfigurationcommand is received via a Physical Downlink Control Channel (PDCCH). 4.The method according to claim 3, wherein the TDD configuration furtherincludes periodicity information, and wherein the method furthercomprises: periodically monitoring PDCCHs for a reconfiguration commandin accordance with the periodicity information.
 5. A user equipment (UE)performing a hybrid automatic repeat request-acknowledgement (HARQ-ACK)procedure in a wireless communication system, the user equipmentcomprising: a transmitter and a receiver; and a processor that:receives, through the receiver, a first TDD (Time Division Duplex)uplink-downlink configuration; receives, through the receiver, a TDDconfiguration, via RRC (Radio Resource Control) signaling, thatcomprises a second TDD uplink-downlink configuration and a HARQreference configuration; reconfigures an uplink-downlink configurationfrom the first TDD uplink-downlink configuration to the second TDDuplink-downlink configuration; receives downlink data in thereconfigured uplink-downlink configuration; and transmits, through thetransmitter, a HARQ-ACK/NACK (HARQ-ACK/Negative-ACK) related to thedownlink data in the reconfigured uplink-downlink configuration based onthe first TDD uplink-downlink configuration and the HARQ referenceconfiguration.
 6. The UE of claim 5, wherein the processor receives,through the receiver, a reconfiguration command and reconfigures theuplink-downlink configuration from the first TDD uplink-downlinkconfiguration to the second TDD uplink-downlink configuration when thereconfiguration command is received.
 7. The UE of claim 6, wherein theprocessor receives, through the receiver, the reconfiguration commandvia a Physical Downlink Control Channel (PDCCH).
 8. The UE of claim 7,wherein the TDD configuration further includes periodicity information,and wherein the processor periodically monitors PDCCHs for areconfiguration command in accordance with the periodicity information.